Method of activating catalysts



Patented Aug. 26, 1941 zataau mz'rnon or ACTIVATING carsusrs Waldo L. Semen, Silver Lake, Ohio, asaignor to The B. F. Goodrich CompanmNew York, N. 1.. a corporation of New York No Drawing. Application August 10, 1988, Serial No. 225,190

Claims.

This invention relates to processes for activating catalysts used in carrying out chemical reactions and particularly to electrolytic processes for activating massive metal catalysts used in hydrogenation processes and for reactivating such catalysts after they have been used and become spent.

In activating a massive metal hydrogenation catalyst by well-known electrolytic methods, the metal catalyst is made the anode of an electrolytic cell and a direct current is passed through the cell until the metal is superficially oxidized.

The metallic oxide then is reduced by treatment with hydrogen to complete the activation of the catalyst.

Heretofore it has been the common practice in such methods to use a dilute aqueous solution of a mild alkali as the electrolyte in the electrolytic cell. For example, 1% to 5% solutions of sodium carbonate, and saturated solutions of the hydroxides of calcium, strontium or barium have been used. Such electrolytes have not been entirely satisfactory, however, for the reason that organic material usually present on the catalysts to be activated is not always fully oxidized by electrolysis carried out in such mild alkali electrolytes. Attempts have been made to obtain complete oxidation of organic material by etfecting the oxidation in an electrolyte of strong alkali, such as sodium or potassium hydroxide solutions but in such attempts the metal catalyst has not been oxidized.

I have now discovered that electrolytic oxidation of metal catalysts may be carried out with a solution of a strong alkali as the electrolyte if the pH of the solution is closely maintained within a narrow range of from 11 to 13.5. Under such conditions organic material present on the catalyst is oxidized and the metal itself likewise is satisfactorily oxidized. Upon subsequent reduction of a catalyst so treated, a highly active hydrogenation catalyst is obtained.

Electrolyte solutions of the required pH value may be prepared simply by dissolving in water from 0.04 to 20 grams of sodium hydroxide per liter of water. A solution containing 0.04 gram of sodium hydroxide per liter will have a pH value of 11 while a solution containing 20 grams per liter will have a pH value of 13.5. Likewise, solutions of potassium hydroxide containing from 0.056 gram per liter to 28 grams per liter will have pH values extending over, the specified range from 11 to 13.5.

When using such solutions, water should be added periodically to replace water lost by electrolysis and by evaporation in order to maintain the pH value .at all times within the specified range. If desired, a buffer solution of appropriate'pH values may be added to assist in main: gailililing the DHTOI the electrolyte at the proper a e.

In many cases, although not essential to the present invention, it is desirable to increase the conductivity of the electrolyte by adding a salt, such as the carbonate, sulfate, chromate, nitrate or chloride of sodium or potassium in a quantity sufllcient to produce the required conductivity. For example, 25 grams to grams of such salts may be added to each liter'of alkali solution. Such addition will raise the-conductivity substantially without appreciably affecting the pH value of the solution.

The following examples serve to illustrate the operation of the present invention:

Example 1 A solution of sodium hydroxide containing 0.4 gram of sodium hydroxide per liter of water and having a pH value of 12 is prepared and introduced into a vessel of suitable size and shape to constitute an electrolytic cell. A sheet of metal,

for example, nickel, is made the cathode of the electrolytic cell. The massive metal catalyst, for example, nickel wire, shavings, chips, etc., contained in a suitable porous container such as a Monel metal wire basket or cage is made the anode of the cell and for convenience is enclosed in a cloth or canvas diaphragm. Considering the catalyst surface to be a solid surface whose dimensions are those of the catalyst cage, a direct current of about 0.05 ampere per square mch at 4 to 10 volts is passed through the electrolyte solution. The passage of the current is maintained until the surface of the turnings and wire are a lustrous black film of oxide or peroxide. This condition indicates a satisfactory reactivation. The oxidized catalyst then "is reduced in an atmosphere of hydrogen by heating for 1 to 2 hours at 200 C. to 250 C. The catalyst so treated will be found to be highly active in hydrogenation processes.

Example 2 In a further specific example of this invention, a massive metal catalyst is subjected to electrolytic anodic oxidation in a manner similar to that described in the foregoing example exceptthat 10% by weight of a salt of an alkali metal, such as sodium carbonate, is added to the solution of the alkali hydroxide constituting the electrolyte.

In a similar manner. new or spent massive metal catalysts composed of such-metals as copper, nickel or cobalt or alloys of these metals with each other or with other metals such as chromium. platinum, palladium, iron or aluminum, as well as mixtures of any of these metals or alloys. may readily be activated.

Specifically. catalysts of copper, mixed copper,

understood that wide variations with relation to materials and operation are possible without departing from the spirit and scope of the invention, as set forth in the following claims.

I claim:

1. The method of activating a massive metal hydrogenation catalyst contaminated with organic materials which comprises subjecting the catalyst to electrolytic oxidation in an aqueous solution of alkali metal hydroxide having a pH of from 11 to 13.5, and thereafter subjecting the oxidized catalyst to a reducing treatment.

2. The method of activating a massive metal hydrogenation catalyst contaminated with organic materials which comprises subjecting the catalyst to electrolytic oxidation inan aqueous solution of sodium hydroxide having a pH of from 11 to 13.5, and thereafter subjecting the oxidized catalyst to treatment with hydrogen at an elevated temperature.

3. The method of activating a massive metal hydrogenation catalyst contaminated with organic materials which comprises subjecting the catalyst to electrolytic oxidation in an aqueous solution of potassium hydroxide having a pH of from '11 to 13.5, and thereafter subjecting the oxidized catalyst to treatment with hydrogen at an elevated temperature.

4. The method of activating a massive metal hydrogenation catalyst contaminated with organic materials which comprises subjecting the catalyst to electrolytic oxidation in an aqueous solution containing an alkali metal hydroxide and an alkali metal salt, said solution having a pH of from 11 to 13.5, and thereafter subjecting the WALDO L. SEMON. 

